1. Field of the Invention
The present invention relates to a machine for the production of a fibrous web, for example a long-fiber paper web or a wet-laid nonwoven web.
2. Description of the Related Art
Machines for the production of a fibrous web, especially a long-fiber or wet-laid nonwoven web and applicable methods to produce the webs, the so-called wet processes, are known in the state of the art. In this wet process, a fiber glass slurry is produced and allocated to a white water stream by adding glass fiber having a fiber length in the range of 6 to 40 mm, preferably 8 to 30 mm, especially 10 to 25 mm to a typical white water in a pulper for dispersion of the glass fiber in the white water by creating the fiber glass slurry having a fiber concentration of approximately 0.2 to 1.0 weight percent. In a sheet forming unit comprising at least one single layer, for example multi-layer, headbox this fiber glass slurry is then brought onto an inclined wire which extends, at least in sections, at an angle to the horizontal, and is dewatered. By dewatering the fiber glass slurry, a fiber glass wet-laid nonwoven material is formed. The formed fiber glass wet-laid nonwoven is then transferred to a binder wire which—at least in segments—is running horizontally or approximately horizontally in a binder wire section. In this binder wire section at least one aqueous binding agent, for example urea-formaldehyde (UF)-resin based binder, is brought onto the wet fiber glass wet-laid nonwoven by means of at least one binder headbox. The surplus binding agent is subsequently sucked off. The aqueous binding agent solution is applied onto the wet fiber glass wet-laid nonwoven by means of a curtain coater or a dip and squeeze applicator. However, other application methods such as spraying are also suitable. The wet fiber glass wet-laid nonwoven that is not yet conglutinated is then transferred into a drying unit including a drying wire for drying and hardening (polymerization) of the binding agent which conglutinates the glass fibers with each other in the fiber glass wet-laid nonwoven. The dryer unit may, for example, be a flow heater or a cylinder dryer or drying conveyor, whereby the fiber glass nonwoven is generally subjected to a temperature of 100 to 250° C., however not for longer than 1 to 2 minutes. Lastly, the fiber glass nonwoven which has a basis weight range of 40 to 200 g/m2 and a binding agent component of 10 to 30% is wound onto winding cores in a winder, resulting in wound rolls in order to then be delivered to subsequent converting or processing stations.
Transfer of the wet and not yet conglutinated fiber glass nonwoven from the binder wire section into the dryer section occurs by means of a roll which is longitudinally corrugated, chrome plated and equipped with its own drive. Here, there is the ever present danger that the roll, when it comes into contact with the very wet fiber glass wet-laid nonwoven which, because of the binding agent application, is very sticky, will very quickly be contaminated with glass fibers. This contamination causes a very high production loss and inherent poor runability since the machine must be completely shut down and the roll which is contaminated with glass fibers must be cleaned. Occasionally, constructions incorporating “Online” roll cleaning are utilized, however the achievable cleaning results both in regard to achievable cleaning quality as well as required cleaning times is very unsatisfactory. Also, the costs associated with such constructions are considerable, not the least of which is necessity to keep a spare roll.
With the current production speeds of up to 350 m/min the roll is also not indexed, since this is not necessary for these production speeds. It is, however, recognized that the fibrous web consisting of the fiber glass wet-laid nonwoven experiences an “unsettled” run in this transfer area, thereby representing a possible hindrance for a future increase in production speeds.
What is needed in the art is an improved suction device of the type referred to at the beginning which largely, for example totally, avoids the cited disadvantages of the current state of the art. Especially the transfer of the wet fibrous web which is not yet conglutinated from the binder wire section into the dryer unit is to be configured process-reliably so that it does not negatively influence the runability of the machine and does not represent a hindrance for a future increase in production speeds.